Stretchable structure of absorbent article and manufacturing method of the same

ABSTRACT

A stretchable structure of an absorbent article has a first sheet layer of a nonwoven fabric; a second sheet layer of a nonwoven fabric and opposed to one side of the first sheet layer. A plurality of elongated elastically stretchable members are provided along the stretchable direction at intervals from each other between the first sheet layer and the second sheet layer. The first sheet layer and the second sheet layer have sheet bonded portions bonded via a hot melt adhesive disposed in a striped pattern that is intermittent in the longitudinal direction of the elastically stretchable members and continuously elongated in the direction intersecting with the elastically stretchable members. One of the first sheet layer and the second sheet layer is a spunbond nonwoven fabric, and the other sheet layer is an air-through nonwoven fabric whose surface on the spunbond nonwoven fabric side is a fluffy surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage application of InternationalApplication PCT/JP2017/006707, filed Feb. 23, 2017, which internationalapplication was published on Oct. 5, 2017, as International PublicationWO 2017/169337 in the Japanese language. The International Applicationclaims priority of Japanese Patent Application No. 2016-069152, filedMar. 30, 2016. The international application and Japanese applicationare both incorporated herein by reference, in entirety.

TECHNICAL FIELD

The present invention relates to a stretchable structure of an absorbentarticle and a method of manufacturing the stretchable structure of anabsorbent article.

BACKGROUND ART

In general, a stretchable structure is provided in an absorbent articleto improve fitting property of each part. For example, in a disposablediaper of an underpants-type or a tape-type, it has been widelypracticed to provide the stretchable structure in a lower torso portionalong the circumferential direction thereof or to provide thestretchable structure in leg portions along the circumferentialdirection thereof. Further, it is widely practiced to provide thestretchable structure in the front-back direction called a“three-dimensional gather” and a “plane gather” over an absorbentarticle including a sanitary napkin as well as a disposable diaper of anunderpants-type and a tape-type.

As a stretchable structure of such an absorbent article, the applicantof the present invention has proposed the stretchable structuredescribed in Patent Literatures 1 and 2. That is, the stretchablestructure of the absorbent article includes a first sheet layer made ofa nonwoven fabric, a second sheet layer made of a nonwoven fabric andopposed to one side of the first sheet layer, and a plurality ofelongated elastically stretchable members provided at intervals fromeach other along the stretchable direction between the first sheet layerand the second sheet layer. The first sheet layer and the second sheetlayer are bonded via a hot melt adhesive disposed in a striped patternintermittent in the longitudinal direction of the elasticallystretchable members and continuously elongated in a directionintersecting with the elastically stretchable members (hereinafter alsoreferred to as a “bonding mode being continuous in the directionintersecting the elastically stretchable members”). In this stretchablestructure, at the time of a natural length state and in a wearing statein which the structure is contracted to some extent, with contraction ofthe elastically stretchable members, portions positioned between sheetbonded portions of the first sheet layer and the second sheet layercontract and are raised in the opposite directions from each other toform pleats. In addition, since the pleats extend straightly along thesheet bonded portions, air permeability and appearance are excellent.

However, it is extremely difficult to stably apply a hot melt adhesive72 in a striped pattern which is intermittent in the longitudinaldirection of elastically stretchable members 19 and elongatedcontinuously in the direction intersecting with the elasticallystretchable members 19 as illustrated in FIG. 22, and since strings 75are stretching out from application portions of the hot melt adhesive 72to a downstream side in the flow direction of the manufacturing line,fine point-like scattering portions 76 are generated, and the like, afirst sheet layer 12S and a second sheet layer 12H are therefore adheredat portions to be pleats (portions between adjacent applications of thehot melt adhesive 72), although these portions are supposed to benon-adhesive portions. This causes a problem that the pleats arecollapsed or irregularly deformed, and the appearance deteriorates.

CITATION LIST Patent Literature

Patent Literature 1: JP 2014-207973 A

Patent Literature 2: JP 2014-198178 A

SUMMARY OF THE INVENTION Technical Problem

Therefore, the main object of the present invention is to preventdeterioration of appearance of pleats due to unintended adhesion.

Solution to Problem

The inventors of the present invention have conducted experiments ofmanufacturing the stretchable structure using various materials for thefirst sheet layer and the second sheet layer and noticed that pleats arenot easily collapsed in the case of using an air-through nonwovenfabric, even if stringiness of the hot melt adhesive occurs. Theinventors did not know the reason at the beginning, but came up with anidea that the fact that the fluffy side of the air-through nonwovenfabric is not easily bonded by a hot melt adhesive results in preventingunintended adhesion under insufficient adhesion conditions such asstringiness and/or scattering of a hot melt adhesive. The presentinvention described below is based on such findings.

<Invention According to Claim 1>

A stretchable structure of an absorbent article, comprising:

a first sheet layer made of a nonwoven fabric; a second sheet layer madeof a nonwoven fabric and opposed to one side surface of the first sheetlayer; and a plurality of elongated elastically stretchable membersprovided along the stretchable direction at intervals from each otherbetween the first sheet layer and the second sheet layer,

wherein the first sheet layer and the second sheet layer have sheetbonded portions bonded via a hot melt adhesive disposed in a stripedpattern that is intermittent in the longitudinal direction of theelastically stretchable members and continuously elongated in thedirection intersecting with the elastically stretchable members, and

either one of the first sheet layer and the second sheet layer is madeof a spunbond nonwoven fabric, and the other sheet layer is made of anair-through nonwoven fabric and has a fluffy surface on the spunbondnonwoven fabric side surface thereof.

(Function and Effect)

The feature of the present invention is that the fluffy surface havingpoor adhesiveness with respect to the hot melt adhesive is intentionallyused as one of adhesive surfaces, and the spunbond nonwoven fabrichaving excellent adhesiveness with respect to the hot melt adhesive isused as the other adhesive surface. As a result, even if stringinessand/or scattering of the hot melt adhesive occurs, under suchinsufficient adhesion conditions, the first sheet layer and the secondsheet layer are not bonded or are peeled off immediately even if beingbonded to some extent. Therefore, deterioration of appearance of thepleats, which would be caused by the unintended adhesion, is effectivelyprevented. In addition, both of the adhesive surfaces made of theair-through nonwoven fabrics would cause a possibility that the sheetbonded portions to be bonded would not be bonded sufficiently. However,in the present invention, the sheet bonded portions are reliably bondedby combining with the spunbond nonwoven fabric having high adhesivenesswith respect to the hot melt adhesive, and consequently, the pleatsexcellent in appearance are formed.

In the present invention, “hot melt adhesive is continuous” means, atintersection portions of the sheet bonded portions and the elasticallystretchable members, that the hot melt adhesive is continuously appliedto both the first sheet layer-side and the second sheet layer-side ofthe elastically stretchable members in the direction intersecting withthe stretchable direction, as well as that the hot melt adhesive iscontinuous in one side due to the elastically stretchable membersinterposed but the hot melt adhesive is discontinuous in the directionintersecting with the stretchable direction on the other side.

<Invention According to Claim 2>

The stretchable structure of an absorbent article according to claim 1,wherein at intersection portions of the sheet bonded portions and theelastically stretchable members, the hot melt adhesive is continuous inthe direction intersecting with the elastically stretchable members onthe spunbond nonwoven fabric side of the elastically stretchablemembers, and the hot melt adhesive is discontinuous in the directionintersecting with the elastically stretchable members on the air-throughnonwoven fabric side of the elastically stretchable members.

(Function and Effect)

Thus, when the hot melt adhesive is continuous on the spunbond nonwovenfabric side of the elastically stretchable members, the adhesiveness atthe sheet bonded portions increases. Furthermore, since the hot meltadhesive is discontinuous on the air-through nonwoven fabric side of theelastically stretchable members, the flexibility of the air-throughnonwoven fabric is not easily impaired.

<Invention According to Claim 3>

The stretchable structure of an absorbent article according to claim 1or 2, wherein the hot melt adhesive has a melt viscosity of 10,000 to40,000 mPa·s at a temperature of 140° C., a melt viscosity of 5,000 to10,000 mPa·s at a temperature of 160° C., and a loop tack adhesivestrength of 10 to 500 g/25 mm

(Function and Effect)

As a hot melt adhesive for forming sheet bonded portions, the hot meltadhesive having a low melt viscosity and a high loop tack adhesivestrength is preferable in that the adhesiveness to a nonwoven fabric isexcellent, but with such hot melt adhesive, stringiness and/orscattering are likely to occur in manufacturing. However, in the presentinvention, unintended adhesion is unlikely to occur even if stringinessand/or scattering of the hot melt adhesive occurs. Therefore, it is alsopossible to use such a hot melt adhesive having high adhesiveness to anonwoven fabric.

<Invention According to Claim 4>

The stretchable structure of an absorbent article according to any oneof claims 1 to 3, wherein the width of each sheet bonded portion in thestretchable direction is 0.5 to 4 mm, and the interval between adjacentsheet bonded portions is 4 to 8 mm

(Function and Effect)

When the sheet bonded portions by the hot melt adhesive are disposed inthese dimensions (the bonding mode being continuous in the directionintersecting the elastically stretchable members), formed pleats areextended straightly and also have sufficient height but rarely fall.

To be more specific, the width in the stretchable direction of eachsheet bonded portion affects the interval between adjacent pleats. Ifthe pleat to be formed is thin, when the width is larger than 4 mm, thespace between adjacent pleats becomes too wide, and individual pleatshave independent appearance. In addition, when the pleats deform forexample, collapse and spread and fall due to a compressive force in thethickness direction, the effect of mutual support of the adjacent pleatsweakens. As a result, resistance with respect to the deformation andrestoration after the deformation also weaken, and fullness becomesinsufficient.

In addition, by merely setting the width of the sheet bonded portion inthe stretchable direction to 0.5 to 4 mm, when the interval betweenadjacent sheet bonded portions is less than 4 mm or more than 8 mm, thefollowing situation will be caused. That is, the interval between theadjacent sheet bonded portions affects the height and width of pleats,and if the interval between adjacent sheet bonded portions is about 2mm, the pleats have poor continuity in the orthogonal direction as withthe case of continuously bonding in the stretchable direction (it has nomeaning to provide sheet bonded portions intermittently in thestretchable direction). If the interval is 3 mm, the pleats straightlyextend in the direction orthogonal to the stretchable direction, but theeffect of mutual support of the adjacent pleats cannot be expected,which results in insufficient fullness. In addition, when the intervalbetween the sheet bonded portions exceeds 8 mm, the pleats are collapsedirregularly due to the compression during wrapping, and the productappearance deteriorates. On the other hand, when the width of the sheetbonded portion in the stretchable direction is 0.5 to 4 mm, and theinterval between the adjacent sheet bonded portions is 4 to 8 mm,sufficient fullness can be finally obtained, and against the compressionduring wrapping, the pleats are unlikely to be collapsed irregularly.

Further, in the case of having the sheet bonded portions with such apattern, stringiness and/or scattering of the hot melt adhesive tends tooccur due to a narrow application width of the hot melt adhesive.Therefore, the present invention is particularly suitable when the sheetbonded portions are formed with such dimensions.

<Invention According to Claim 5>

The stretchable structure of an absorbent article according to any oneof claims 1 to 4, wherein the absorbent article is an underpants-typedisposable diaper, in which an outer member disposed in a front body anda back body and an inner member attached to the outer member andincluding an absorber are provided, both side edges of the outer memberof the frond body and both side edges of the outer member of the backbody are bonded to each other, a range corresponding in the front-backdirection to the bonded side edges is an annular lower torso portion,and a waist opening and a pair of right and left leg openings areformed, and

the stretchable structure is provided in a region including at leastboth sides in the width direction of the inner member in the outermember such that the elastically stretchable members extend along thewidth direction, and the air-through nonwoven fabric is on the outsideand the spunbond nonwoven fabric is on the inside.

(Function and Effect)

As described above, the stretchable structure according to the presentinvention is suitable for the region including at least both sides inthe width direction of the inner member in the outer member of theunderpants-type disposable diaper. In particular, since the outersurface of the outer member is made of the air-through nonwoven fabric,the appearance of pleats on the outer surface of the product is hardlydeteriorated, and the outer surface of the product is rich inflexibility when touched with hand.

<Invention According to Claim 6>

A method of manufacturing a stretchable structure of an absorbentarticle, comprising:

using a first sheet layer made of either one of a spunbond nonwovenfabric and an air-through nonwoven fabric and a second sheet layer madeof the other nonwoven fabric;

sandwiching a plurality of elongated elastically stretchable membersprovided along the stretchable direction at intervals from each otherbetween the first sheet layer and the second sheet layer, in which afluffy surface of the air-through nonwoven fabric is disposed to facethe spunbond nonwoven fabric; and

forming sheet bonded portions by bonding the first sheet layer and thesecond sheet layer via a hot melt adhesive disposed in a striped patternthat is intermittent in a longitudinal direction of the elasticallystretchable members and continuously elongated in a directionintersecting with the elastically stretchable members.

(Function and Effect)

The same functions and effects as those obtained in the inventionaccording to claim 1 are obtained.

<Invention According to Claim 7>

The method of manufacturing the stretchable structure of an absorbentarticle according to claim 6, wherein in the forming of the sheet bondedportions, the hot melt adhesive is applied to the air-through nonwovenfabric side surface of the spunbond nonwoven fabric in the stripedpattern that is intermittent in the longitudinal direction of theelastically stretchable members and continuously elongated in thedirection intersecting with the elastically stretchable members, and

the hot melt adhesive is not applied to the fluffy surface of theair-through nonwoven fabric.

(Function and Effect)

The same functions and effects as those obtained in the inventionaccording to claim 2 are obtained.

<Invention According to Claim 8>

The method of manufacturing the stretchable structure of an absorbentarticle according to claim 6 or 7,

wherein the hot melt adhesive has a melt viscosity of 10,000 to 40,000mPa·s at a temperature of 140° C., a melt viscosity of 5,000 to 10,000mPa·s at a temperature of 160° C., and a loop tack adhesive strength of10 to 500 g/25 mm.

(Function and Effect)

The same functions and effects as those obtained in the inventionaccording to claim 3 are obtained.

<Invention According to Claim 9>

The method of manufacturing the stretchable structure of an absorbentarticle according to any one of claims 6 to 8, comprising:

a step of applying the hot melt adhesive in which at least one of thefirst sheet layer and the second sheet layer is brought into contactwith an engraved roll such that a circumferential direction of theengraved roll is a stretchable direction, and the hot melt adhesive,which is held in the striped pattern that is intermittent in thecircumferential direction and continuous in the axial direction on theouter peripheral surface of the engraved roll, is transferred on atleast one of the first sheet layer and the second sheet layer; and

a step of performing pressure bonding in which the elasticallystretchable members are sandwiched between the first sheet layer and thesecond sheet layer on at least one of which the hot melt adhesive istransferred,

wherein in the step of applying the hot melt adhesive, on the outerperipheral surface of the engraved roll, the application width in thecircumferential direction of the hot melt adhesive is set to 0.5 to 4mm, and the interval between the adjacent applications in thecircumferential direction of the hot melt adhesive is set to 4 to 8 mm.

(Function and Effect)

The same functions and effects as those obtained in the inventionaccording to claim 4 are obtained. Further, in such a patternapplication by the transfer with the roll, although the applicationwidth of the hot melt adhesive can be narrowed, stringiness and/orscattering are likely to occur. Therefore, this claim is particularlysuitable for applying the present invention.

Advantage Effects of Invention

As described above, according to the present invention, it is possibleto prevent deterioration of appearance of pleats due to unintendedadhesion, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view illustrating the inner surface of anunderpants-type disposable diaper in a state where a diaper is spread.

FIG. 2 is a plan view illustrating the outer surface of anunderpants-type disposable diaper in a state where a diaper is spread.

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1.

FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 1.

FIG. 5(a) is a cross-sectional view taken along line 5-5 in FIG. 1. FIG.5(b) is a cross-sectional view taken along line 2-2 in FIG. 1.

FIG. 6 is a perspective view of an underpants-type disposable diaper.

FIG. 7 is a plan view illustrating an outer member in a spread state.

FIG. 8 is a plan view illustrating an outer member in a spread state.

FIG. 9 is a plan view illustrating an outer member in a spread state.

FIG. 10(a) is a cross-sectional view taken along line 5-5 in FIG. 1.FIG. 10(b) is a cross-sectional view taken along line 2-2 in FIG. 1.

FIG. 11(a) is a plan view of a stretchable structure in a spread state.FIG. 11(b) is a cross-sectional view taken along line 6-6 in a naturallength state. FIG. 11(c) is a cross-sectional view taken along line 6-6in a state stretched to some extent.

FIG. 12(d) is a cross-sectional view taken along line 8-8 in FIG. 11.FIG. 12(e) is a cross-sectional view taken along line 7-7 in FIG. 11.FIG. 12(f) is a cross-sectional view taken along line 9-9 in FIG. 11.FIG. 12(g) is a cross-sectional view taken along line 10-10 in FIG. 11.

FIG. 13(a) is a plan view of a stretchable structure in a spread state.FIG. 13(b) is a cross-sectional view taken along line 6-6 in a naturallength state. FIG. 13(c) is a cross-sectional view taken along line 6-6in a state stretched to some extent.

FIG. 14(d) is a cross-sectional view taken along line 8-8 in FIG. 13.FIG. 14(e) is a cross-sectional view taken along line 7-7 in FIG. 13.FIG. 14(f) is a cross-sectional view taken along line 9-9 in FIG. 13.FIG. 14(g) is a cross-sectional view taken along line 10-10 in FIG. 13.

FIG. 15(a) is a plan view of a stretchable structure in a spread state.FIG. 15(b) is a cross-sectional view taken along line 6-6 in a naturallength state. FIG. 15(c) is a cross-sectional view taken along line 6-6in a state stretched to some extent.

FIG. 16(d) is a cross-sectional view taken along line 8-8 in FIG. 15.FIG. 16(e) is a cross-sectional view taken along line 7-7 in FIG. 15.FIG. 16(f) is a cross-sectional view taken along line 9-9 in FIG. 15.FIG. 16(g) is a cross-sectional view taken along line 10-10 in FIG. 15.

FIG. 17 is a plan view of a stretchable structure in a spread state.

FIG. 18 is a plan view illustrating a main part of an outer member in aspread state.

FIG. 19 is a manufacturing flow of the stretchable structure.

FIG. 20 is a perspective view of a cutting device.

FIG. 21 is an enlarged plan view of a main part indicating variousembodiments for cutting in a non-stretchable region.

FIG. 22 is an enlarged plan view of a main part conceptually indicatingstringiness and scattering of a hot melt adhesive.

FIG. 23 is an explanatory view of a test piece of a peel strengthmeasurement test.

FIG. 24 is an explanatory view of a peel strength measurement test.

FIG. 25 is an explanatory view of a test piece of a holding powermeasurement test.

FIG. 26 is an explanatory view of a holding power measurement test.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIGS. 1 to 6 illustrate an example of an underpants-type disposablediaper 100. This underpants-type disposable diaper 100 is composed of anouter member 12 disposed in an outer surface (back surface side) of aproduct and an inner member 200 attached to the outer member 12. Thereference sign 201 denotes a region where the inner member 200 and theouter member 12 are fixed. The reference sign Y denotes the maximumlength of the diaper. The reference sign X denotes the maximum width ofthe diaper.

The inner member 200 is a portion to absorb and hold excrement such asurine, and the outer member 12 is a portion to attach the inner member200 to the body of a wearer. In addition, the dotted portions in thecross-sectional view indicate bonded portions to bond respectivecomponent members, and the bonded portions are formed by, for examplesolid, bead, curtain, summit, or spiral application of a hot meltadhesive or the like.

(Inner Member)

The inner member 200 can have an arbitrary shape, but in the illustratedembodiment, it is rectangular. As illustrated in FIGS. 3 to 5, the innermember 200 is provided with a top sheet 30 which is in contact with theskin, a liquid impervious sheet 11, and an absorbent element 50interposed therebetween, and is a main unit section that plays a role ofan absorbent function. The reference sign 40 denotes an intermediatesheet (second sheet) provided between the top sheet 30 and the absorbentelement 50 in order to promptly transfer liquid having permeated throughthe top sheet 30 to the absorbent element 50. The reference sign 60denotes three-dimensional gathers 60 provided on both sides of the innermember 200 and standing on the skin side of a wearer in order to preventexcrement from leaking to both sides of the inner member 200.

(Top Sheet)

The top sheet 30 has a property of permeating liquid, and examples ofthe top sheet 30 include a perforated or nonporous nonwoven fabric and aporous plastic sheet. Among them, a raw fiber of the nonwoven fabric isnot particularly limited. Examples of the raw fiber include syntheticfibers such as olefin such as polyethylene and polypropylene, polyester,and polyamide, regenerated fibers such as rayon and cupra, naturalfibers such as cotton, and mixed fibers and composite fibers in whichtwo or more of these are used. Further, the nonwoven fabric may bemanufactured by any processing. Examples of the processing methodinclude known methods such as a spunlace method, a spunbond method, athermalbond method, a meltblown method, a needlepunch method, an airthrough method, and a pointbond method. For example, if flexibility anddrapeability are required, the spunbond method and the spunlace methodare preferable processing methods, and if bulkiness and softness arerequired, the air through method, the pointbond method, and thethermalbond method are preferable processing methods.

Further, the top sheet 30 may be made of one sheet or a laminated sheetobtained by bonding two or more sheets. Similarly, the top sheet 30 maybe composed of one sheet or two or more sheets with respect to the planedirection.

In the case of providing the three-dimensional gathers 60, it ispreferable that both side edges of the top sheet 30 are extended betweenthe liquid impervious sheet 11 and the three-dimensional gathers 60 andto the back face of the absorbent element 50 and bonded to the liquidimpervious sheet 11 and the three-dimensional gathers 60 with a hot meltadhesive or the like to prevent liquid permeation.

(Intermediate Sheet)

An intermediate sheet (also called a “second sheet”) 40 can be providedbetween the top sheet 30 and the absorbent element 50. This intermediatesheet 40 not only improves the absorption performance by an absorber 56by immediately moving liquid to the absorber 56 side, but also preventsthe absorbent liquid from returning from the absorber 56 and makes thesurface of the top sheet 30 dry. The intermediate sheet 40 can also beomitted.

Examples of the intermediate sheet 40 include the same material as thetop sheet 30, a spunlace, a spunbond, SMS, a pulp nonwoven fabric, amixed sheet of pulp and rayon, a pointbond, or a crepe paper. Inparticular, an air-through nonwoven fabric is preferable because it isbulky. It is preferable to use a composite fiber having a core-sheathstructure for the air-through nonwoven fabric. In this case, resin usedfor the core may be polypropylene (PP), but polyester (PET) having highrigidity is preferable. The basis weight is preferably 20 to 80 g/m²,more preferably 25 to 60 g/m². The fineness of the raw fiber of thenonwoven fabric is preferably 2.2 to 10 dtex. To increase the bulkinessof the nonwoven fabric, it is also preferable to use eccentric fibers,hollow fibers, eccentric and hollow fibers, whose core is not in thecenter, as mixed fibers of all or a part of the raw material fibers.

The intermediate sheet 40 in the illustrated embodiment is disposed atthe center shorter than the width of the absorber 56, but may beprovided over the maximum width. The length of the intermediate sheet 40in the longitudinal direction may be the same as the length of theabsorber 56 or may be within a short length range centered on the liquidreceiving area.

(Liquid Impervious Sheet)

The material of the liquid impervious sheet 11 is not particularlylimited, but examples of the material include a plastic film made of anolefin resin such as polyethylene and polypropylene, a laminatednonwoven fabric having a plastic film on the surface of a nonwovenfabric, and a laminated sheet obtained by bonding nonwoven fabrics orthe like on a plastic film. In the liquid impervious sheet 11, in recentyears, it is preferable to use a material having liquid impermeabilityand moisture permeability that has been favorably used from theviewpoint of prevention of stuffiness. As the moisture-permeable plasticfilm, a microporous plastic film is widely used. The microporous plasticfilm is obtained by stretching a sheet in a monoaxial or biaxialdirection after forming the sheet by kneading an inorganic filler in anolefin-based resin such as polyethylene or polypropylene. In addition tothis, a nonwoven fabric sheet of microdenier fiber and a liquidimpervious sheet without a plastic film having reinforcedleakage-resistance achieved by applying heat and pressure to reduce thegaps between the fibers or by application with super absorbent resin, ahydrophobic resin, or a water repellent agent can also be used as theliquid impervious sheet 11.

To enhance leakage resistance, the liquid impervious sheet 11 can alsobe disposed around the both side faces of the absorbent element 50 toextend to the both sides of the side surface of the top sheet 30 of theabsorbent element 50.

Further, on the inside of the liquid impervious sheet 11, in particular,on the side surface of the absorber 56, an excretion indicator thatchanges its color due to absorption of a liquid component can beprovided.

(Three-Dimensional Gather)

The three-dimensional gathers 60 are strip-shaped members extendingalong the both side edges of the inner member 200 in the front-backdirection. The three-dimensional gather 60 is provided to block fluidexcretion (urine, loose stools, etc.) moving on the top sheet 30 in thelateral direction and to prevent lateral leakage. The three-dimensionalgather 60 according to the present embodiment is provided so as to standupright from the side portion of the inner member 200, the root-sideportion stands obliquely toward the center-side in the width direction,and the portion closer to the tip side than the intermediate portionstands obliquely toward the outside in the width direction. Althoughthis embodiment is a surface contact type three-dimensional gather, aline contact type three-dimensional gather (not illustrated) which isnot folded back outward in the width direction can also be used.

To be more specific, the three-dimensional gather 60 includes a beltshaped gather sheet 62 having a length equal to the length in thefront-back direction of the inner member 200 and folded back in two inthe width direction, and a plurality of elongated elasticallystretchable members 63 fixed along the longitudinal direction withintervals in the width direction in a stretched state between sheets inthe folded portion and the neighboring portions. An end portion on theopposite side to the folded portion in the width direction in thethree-dimensional gather 60 is an attachment portion 65 fixed to therear surface of the side edge portion of the inner member 200. A portionother than the attachment portion 65 is a protruding portion 66 (aportion on the folded portion side) protruding from the attachmentportion 65. The both ends of the protruding portion 66 in the front-backdirection extend from the attachment portion 65 to the surface of theside portion of the top sheet 30 through the side of the inner member200, and the both ends are fallen portions fixed by a fixing means suchas the hot melt adhesive 67 with respect to the surface of the sideportion of the top sheet 30. The intermediate portion in the front-backdirection of the protruding portion 66 is a non-fixed free portion, andthe elongated elastically stretchable members 63 along the front-backdirection are fixed in a stretched state at least over the entirefront-back direction of the free portion.

As the gather sheet 62, a nonwoven fabric which is flexible andexcellent in uniformity and concealing property such as a spunbondnonwoven fabric (SS, SSS, etc.), SMS nonwoven fabric (SMS, SSMMS etc.),meltblown nonwoven fabric, and on which a water repellent process isperformed by silicone as necessary, can be preferably used, and thefiber basis weight is preferably set to about 10 to 30 g/m². As theelongated elastically stretchable member 63, a rubber thread and thelike can be used. When a spandex rubber thread is used, the fineness ispreferably 470 to 1240 dtex, more preferably 620 to 940 dtex. Thestretch rate at the time of fixing is preferably from 150 to 350%, morepreferably from 200 to 300%. The term “stretch rate” means a value whenthe natural length is taken as 100%. As illustrated in the drawing, awaterproof film 64 may be interposed between gather sheets folded intwo.

The number of the elongated elastically stretchable members 63 providedin the free portion of the three-dimensional gather 60 is preferably twoto six, more preferably three to five. An appropriate arrangementinterval 60 d is 3 to 10 mm. With such a configuration, a range in whichthe elongated elastically stretchable members 63 are disposed easilycomes into surface contact with the skin. The elongated elasticallystretchable members 63 may be disposed not only on the tip side but alsoon the root side.

The target to which the attachment portion 65 of the three-dimensionalgather 60 is fixed can be an appropriate member, such as the top sheet30, the liquid impervious sheet 11, and the absorbent element 50 in theinner member 200.

In the three-dimensional gathers 60 formed as described above, acontraction force of the elongated elastically stretchable members 63acts so as to bring both ends in the front-back direction close to eachother, but both ends in the front-back direction of the protrudingportions 66 are fixed in a fallen state, and spaces between the bothends are non-fixed free portions. Therefore, only the free portionsstand so as to come into contact with the body side as illustrated inFIG. 3. Particularly, when the attachment portions 65 are positioned onthe back side of the inner member 200, the three-dimensional gathers 60stand up so as to open outward in the width direction at and around acrotch portion, such that the three-dimensional gathers 60 come intosurface contact with leg portions, and therefore the fit is improved.

Unlike the illustrated embodiment, three-dimensional gathers can bedoubly (in two rows) provided on each of the left and right sides of theinner member 200.

(Absorbent Element)

The absorbent element 50 has the absorber 56 and a wrapping sheet 58wrapping the entire absorber 56. The wrapping sheet 58 can also beomitted.

(Absorber)

The absorber 56 can be formed of an assembly of fibers. As this fiberassembly, besides those obtained by accumulating short fibers such asfluff pulp and synthetic fibers, a filament assembly obtained by openingtows (fiber bundles) of synthetic fibers such as cellulose acetate asrequired can also be used. When fluff pulp or short fibers areaccumulated, fiber basis weight can be set to, for example, about 100 to300 g/m², and in the case of a filament assembly, fiber basis weight canbe set to about 30 to 120 g/m². In the case of a synthetic fiber, thefineness is, for example, 1 to 16 dtex, preferably 1 to 10 dtex, morepreferably 1 to 5 dtex. In the case of filament assembly, the filamentsmay be non-crimped fibers, but are preferably crimped fibers. The degreeof crimp of the crimped fiber can be, for example, about 5 to 75,preferably 10 to 50, and more preferably about 15 to 50 per inch. Inaddition, crimped fibers which are uniformly crimped are often used. Itis preferable to disperse and hold the super absorbent polymer particlesin the absorber 56.

The absorber 56 may have a rectangular shape, and, as illustrated inFIGS. 1 and 2, preferably has a shape similar to the outline of anhourglass where between the front end portion and the back end portion,a narrowing portion is disposed having a width smaller than that of thefront end portion and that of the back end portion, since the fit of theabsorber 56 and the three-dimensional gathers 60 to the legs isimproved.

Further, although the size of the absorber 56 can be appropriatelydetermined, it is preferable that the absorber 56 extends to or near theperipheral edge portion of the inner member in the front-back directionand the width direction. The reference sign 56X denotes the width of theabsorber 56.

(Super Absorbent Polymer Particle)

The absorber 56 can contain super absorbent polymer particles partiallyor entirely. The super absorbent polymer particles include “powder” inaddition to “particles”. The particle sizes of super absorbent polymerparticles may be those used in similar types of absorbent articles.Preferred particle sizes are desirably 1000 μm or less, in particular,150 to 400 μm. The material of the super absorbent polymer particle isnot particularly limited, but a material having a water absorptioncapacity of 40 g/g or more is suitable. Examples of the super absorbentpolymer particle include starch-based, cellulose-based, and syntheticpolymer-based particle, and starch-acrylic acid (salt) graft copolymer,saponified starch-acrylonitrile copolymer, crosslinked sodiumcarboxymethyl cellulose, and acrylic acid (salt) polymer. The superabsorbent polymer particles have preferably a generally used particulateform. However, the super absorbent polymer particles may have anotherform.

The super absorbent polymer particles having a water absorption rate of40 seconds or less are preferably used. When the water absorption rateexceeds 40 seconds, the liquid supplied into the absorber 56 tends toeasily return to the outside of the absorber 56.

As the super absorbent polymer particles, those having a gel strength of1,000 Pa or more are preferably used. This makes it possible toeffectively suppress the sticky feeling after absorbing the liquid evenin a bulky absorber 56.

The basis weight of the super absorbent polymer particles can beappropriately determined according to the absorption amount required forthe use of the absorber 56. Therefore, although it cannot be saidunconditionally, the basis weight can be 50 to 350 g/m². When the basisweight of the polymer is less than 50 g/m², it is difficult to ensurethe absorption amount. When it exceeds 350 g/m², the effect issaturated.

If necessary, the super absorbent polymer particles can adjust aspraying density or a spraying amount in the planar direction of theabsorber 56. For example, it is possible to increase the spraying amountin an excretory site of liquid compared to the other sites. Whenconsidering the difference between men and women, it is possible toincrease the spray density (amount) on the front side for men and toincrease the spray density (amount) at the center for women. Further, aportion without polymer can be provided locally (for example, in a spotshape) in the planar direction of the absorber 56.

(Wrapping Sheet)

When the wrapping sheet 58 is used, tissue paper, particularly crepepaper, nonwoven fabric, polyethylene laminated nonwoven fabric, a sheetwith small openings can be used as the material. However, it isdesirable that the sheet from which the super absorbent polymerparticles do not come off is used. When a nonwoven fabric is used inplace of crepe paper, a hydrophilic SMS nonwoven fabric (SMS, SSMMS,etc.) is particularly suitable, and polypropylene,polyethylene/polypropylene composite material and the like can be usedas the material. The basis weight is desirably 5 to 40 g/m², inparticular, desirably 10 to 30 g/m².

The wrapping mode of the wrapping sheet 58 can be appropriatelydetermined. However, from the viewpoints of ease of manufacturing andprevention of leakage of super absorbent polymer particles from thefront and back end edges, it is preferable that the wrapping sheet 58 iswound around in a cylindrical shape so as to surround the front and backsurfaces and both side surfaces of the absorber 56, the front and backedge portions are protruded from the front and back of the absorber 56,and the protruding portions are collapsed in the thickness direction tobond by a bonding means such as a hot melt adhesive.

(Outer Member)

The outer member 12 has a portion disposed in a front body F extendingfrom the center in the front-back direction to the ventral side and aportion disposed in a back body B extending from the center in thefront-back direction to the dorsal side. Both side edges of the frontbody F and both side edges of the back body B are bonded to each other,and as illustrated in FIG. 6, a waist opening WO through which the torsoof a wearer passes and a pair of left and right leg openings LO throughwhich the legs are passed are formed. The reference sign 12A denotes abonded side edge portion (hereinafter, this portion is also referred toas a “side seal portion”). The crotch portion means the center in thefront-back direction from the waist edge of the front body F to thewaist edge of the back body B in a spread state, and the front sideportion and the back side portion from the center are the front body Fand the back body B, respectively.

The outer member 12 has a lower torso portion T and an intermediateportion L. The lower torso portion T is defined as a range in thefront-back direction from the waist opening WO to the upper ends of theleg openings LO. The intermediate portion L is defined as a range in thefront-back direction of a portion forming the leg openings LO (betweenthe region in the front-back direction having a side seal portion 12A ofthe front body F and the region in the front-back direction having aside seal portion 12A of the back body B). The lower torso portion T canbe divided into a waist portion W which conceptually forms an edgeportion of the waist opening and an under-waist portion U which is aportion lower than the waist portion W. Normally, in the lower torsoportion T, in the case of having a boundary where the stretching stressalong the width direction changes (for example, the fineness and stretchrate of the elastically stretchable members change), a portion nearer tothe waist opening WO than a boundary closest to the waist opening WO isthe waist portion W. When there is no such boundary, the waist openingWO side of the absorber 56 or the waist opening WO side of the innermember 200 is the waist portion W. The lengths of such portions in thelongitudinal direction vary depending on the size of a product and canbe appropriately determined. For example, the waist portion W can be setto 15 to 40 mm, and the under-waist portion U can be set to 65 to 120mm. On the other hand, both side edges of the intermediate portion L arenarrowed along the periphery of the legs of a wearer, and they are sitesthrough which the wearer's legs pass. As a result, the outer member 12is substantially hourglass-shaped as a whole. The degree of narrowing ofthe outer member 12 can be appropriately determined, and to obtain aclean appearance as in the embodiments illustrated in FIGS. 1 to 6, thenarrowest portion is preferably narrower than the width of the innermember 200, but the narrowest portion may be determined to be equal toor greater than the width of the inner member 200.

As illustrated in FIGS. 3 to 5, front and back surfaces of the outermember 12 are formed by a first sheet layer 12S made of a nonwovenfabric and a second sheet layer 12H formed of a nonwoven fabric. Toenhance the fit to the body, the outer member 12 has a continuousstretchable region A3, a non-stretchable region A1, and intermittentstretchable regions A2. The continuous stretchable region A3 continuesin the width direction in the area nearer to the waist opening WO thanto the absorber 56. The non-stretchable region A1 is provided in themiddle in the width direction in the range in the front-back directionhaving the absorber 56. The intermittent stretchable regions A2 areprovided on both sides in the width direction of the non-stretchableregion A1. Between the first sheet layer 12S and the second sheet layer12H in the continuous stretchable region A3 and the intermittentstretchable regions A2, elongated elastically stretchable members 19 (15to 17) such as rubber threads are attached at a predetermined stretchrate along the width direction to be stretchable in the width direction(the width direction is a stretchable direction). As the elongatedelastically stretchable member 19, synthetic rubber may be used, andalso natural rubber may be used. The continuous stretchable region A3may be formed over the entire width direction in a part or whole of arange in the front-back direction having the non-stretchable region A1and the intermittent stretchable regions A2 in the illustratedembodiment. Alternatively, the range in the front-back direction of thenon-stretchable region A1 in the illustrated embodiment may be extendedtoward the waist side or the crotch side.

To be more specific about the illustrated embodiment, the waist portionW of the outer member 12 is formed as the continuous stretchable regionA3, and between the first sheet layer 12S and the second sheet layer12H, a plurality of waist portion elastically stretchable members 17 isattached with intervals in the front-back direction in a stretched statealong the width direction at a predetermined stretch rate so as tocontinue over the whole of the width direction. One or a plurality ofthe waist portion elastically stretchable members 17 disposed adjacentto the under-waist portion U may overlap with the absorber 56. A portionadjacent to the under-waist portion U in the waist portion W may be aregion having the non-stretchable region A1 and the intermittentstretchable regions A2 similarly to the under-waist portion U. As thewaist portion elastically stretchable members 17, about 3 to 22 rubberthreads having a fineness of 155 to 1880 dtex, particularly about 470 to1240 dtex (in the case of synthetic rubber), (in the case of naturalrubber, a cross-sectional area of about 0.05 to 1.5 mm², particularlyabout 0.1 to 1.0 mm²) are preferably attached with intervals of 5 to 20mm, particularly 8 to 16 mm, at a stretch rate of 150 to 400%,particularly about 220 to 320%. Further, it is not necessary to make allof the waist portion elastically stretchable members 17 have the samefineness and stretch rate. For example, the fineness and the stretchrate of the elastically stretchable members 17 may be different at theupper portion and the lower portion of the waist portion W.

In addition, a plurality of under-waist portion elastically stretchablemembers 15 made of elongated elastically stretchable members is attachedwith intervals in the front-back direction in a stretched state alongthe width direction at a predetermined stretch rate so as to continueover the entire width direction in the upper side and both sides in thewidth direction of the non-stretchable region A1, except in thenon-stretchable region A1, between the first sheet layer 12S and thesecond sheet layer 12H of the under-waist portion U of the outer member12. As the under-waist portion elastically stretchable members 15, it ispreferable that about 5 to 30 rubber threads having a fineness of 155 to1880 dtex, particularly about 470 to 1240 dtex (in the case of syntheticrubber), (in the case of natural rubber, a cross-sectional area of about0.05 to 1.5 mm², particularly about 0.1 to 1.0 mm²) are attached withintervals of 5 to 20 mm, particularly 8 to 16 mm, at a stretch rate of200 to 350%, particularly about 240 to 300%.

Further, a plurality of intermediate portion elastically stretchablemembers 16 made of elongated elastically stretchable members is attachedwith intervals in the front-back direction in a stretched state alongthe width direction at a predetermined stretch rate so as to continueover the entire width direction in the both sides in the width directionof the non-stretchable region A1, except in the non-stretchable regionA1, between the first sheet layer 12S and the second sheet layer 12H ofthe intermediate portion L of the outer member 12. As the cover portionelastically stretchable members 16, it is preferable that about 2 to 10rubber threads having a fineness of 155 to 1880 dtex, particularly about470 to 1240 dtex (in the case of synthetic rubber), (in the case ofnatural rubber, a cross-sectional area of about 0.05 to 1.5 mm²,particularly about 0.1 to 1.0 mm²) are attached with intervals of 5 to20 mm, particularly 8 to 16 mm, at a stretch rate of 150 to 300%,particularly 180 to 260%.

As with the intermittent stretchable region A2 in the illustratedembodiment, in the case where the elastically stretchable members 19(the under-waist portion elastically stretchable members 15 and theintermediate portion elastically stretchable members 16 in theillustrated embodiment) provided in the outer member 12 are provided onboth sides in the width direction of the non-stretchable region A1,except in the non-stretchable region A1, contraction of the absorber 56in the width direction is prevented in the non-stretchable region A1.Therefore, it is preferable that the non-stretchable region A1 is theregion at the intermediate region in the width direction includingpartly or totally a portion overlapping in the width direction with theabsorber 56 (more preferably including totally the region 201 where theinner member 200 and the outer member 12 are fixed), and theintermittent stretchable regions A2 are the entire regions on both sidesin the width direction of the non-stretchable region, reaching the sideseal portions 12A.

(Divided Structure of Outer Member)

In the illustrated example, the outer member 12 has a structurecontinuously covering from the front body F to the back body B, but theouter member can have another structure where the outer member disposedin the front body F and the outer member disposed in the back body B maynot be continuous but separated (not illustrated). In this case, acrotch outer member can be attached for covering the portion exposedbetween the outer member disposed in the front body F and the outermember disposed in the back body B on the outer surface of the innermember 200. As the crotch outer member, the same materials as those usedfor the outer member described above can be used.

(About Stretchable Structure)

In the underpants-type disposable diaper, the stretchable structure ofthe present invention is applied in the region from the waist portion Wto the intermediate portion L. That is, as illustrated in FIGS. 4, 7,and 11, a plurality of elongated elastically stretchable members 19 isdisposed with intervals from each other along the stretchable directionbetween the first sheet layer 12S and the second sheet layer 12H. Bothend portions 19 f of the elastically stretchable members 19 are fixedend portions 19 f at which the elastic stretchable members are fixed toat least one of the first sheet layer 12S and the second sheet layer 12Hvia the first hot melt adhesive 71. The first sheet layer 12S and thesecond sheet layer 12H have the sheet bonded portions 70 bonded via thesecond hot melt adhesive 72 which is disposed in the striped patterncontinuing intermittently in the longitudinal direction of theelastically stretchable members 19 and continuously elongated in thedirection intersecting with the elastically stretchable members 19 in arange at least in the stretchable direction corresponding to spacesbetween the both end portions 19 f of the elastically stretchablemembers 19.

(Hot Melt Adhesive)

Examples of the first hot melt adhesive 71 and the second hot meltadhesive 72 include, but are not limited to, adhesives of the EVA type,adhesive rubber type (elastomer type), olefin type, andpolyester/polyamide. The first hot melt adhesive 71 and the second hotmelt adhesive 72 may be the same. At the intersection positions of thesecond hot melt adhesive 72 and the elastically stretchable members 19,since the elastically stretchable members 19 can be fixed to at leastone of the first sheet layer 12S and the second sheet layer 12H via thesecond hot melt adhesive 72, as long as the elastically stretchablemembers 19 can be sufficiently fixed only with the second hot meltadhesive 72, it is not necessary to provide the first hot melt adhesive71.

When both of the first hot melt adhesive 71 and the second hot meltadhesive 72 are used, it is preferable that the holding power of thefirst hot melt adhesive 71 is higher than the holding power of thesecond hot melt adhesive 72. In particular, the holding power of thefirst hot melt adhesive 71 is preferably greater than 120 minutes, andthe holding power of the second hot melt adhesive 72 is preferably 30 to90 minutes.

Further, in general, since a hot melt adhesive having a high meltviscosity generally has the high holding power, it is desirable that themelt viscosity of the first hot melt adhesive 71 is higher than the meltviscosity of the second hot melt adhesive 72. To be more specific, thefirst hot melt adhesive 71 preferably has a melt viscosity of 10,000 to40,000 mPa·s at a temperature of 140° C. and a melt viscosity of 5,000to 10,000 mPa·s at a temperature of 160° C., and the second hot meltadhesive 72 preferably has a melt viscosity of 3,000 to 7,000 mPa·s at atemperature of 140° C. and a melt viscosity of 1,000 to 4,000 mPa·s at atemperature of 160° C.

Further, since the hot melt adhesive having high loop tack adhesivestrength is suitable for bonding nonwoven fabrics to each other, it isdesirable that the loop tack adhesive strength of the second hot meltadhesive 72 is higher than the loop tack adhesive strength of the firsthot melt adhesive 71. Specifically, the loop tack adhesive strength ofthe first hot melt adhesive 71 is preferably 10 to 500 g/25 mm, and theloop tack adhesive strength of the second hot melt adhesive 72 ispreferably 1,000 g/25 mm or more.

It is more preferable that the peel strength of the first hot meltadhesive 71 is 100 cN/25 mm or more in both the longitudinal and lateraldirections, and the peel strength of the second hot melt adhesive 72 is100 cN/25 mm or more in both the longitudinal and lateral directions.

The first hot melt adhesive 71 that satisfies such requirements can beeasily obtained from hot melt adhesive manufacturers.

Although the basis weight (application amount) of the first hot meltadhesive 71 and the second hot melt adhesive 72 can be appropriatelydetermined, it is preferable that the basis weight is in the range of 3to 30 g/m², in particular in the range of 10 to 20 g/m².

(Fixing of Elastically Stretchable Members)

As illustrated in FIGS. 4, 7 and 11, in the elastically stretchablemembers 19 in the continuous stretchable region A3 and those in theintermittent stretchable region A2, the both end portions 19 f in thewidth direction are the fixed end portions 19 f fixed to the first sheetlayer 12S and the second sheet layer 12H via the first hot melt adhesive71. In the case where the elastically stretchable members 19 areprovided on the both sides in the width direction of the intermediateportion in the width direction of the outer member 12, except in theintermediate portion as shown in the illustrated embodiment, the bothend portions 19 f of the elastically stretchable members 19 at the bothsides in the width direction of the intermediate portion are defined asthe fixed end portions 19 f, respectively. In the case of theelastically stretchable members 19 continuing over the entire widthdirection of the outer member 12, the portions positioned at the bothend portions 19 f in the width direction of the outer member 12 of theelastically stretchable members 19 are defined as the fixed end portions19 f.

As illustrated in FIGS. 7, 8, 11 and 13, the first hot melt adhesive 71is disposed intermittently in a direction orthogonal to the elasticallystretchable members 19 and disposed only at positions overlapping withthe elastically stretchable members 19. Further, as illustrated in FIGS.9 and 15, the first hot melt adhesive 71 can be disposed in a patterncontinuing in the front-back direction so as to extend over the endportions of the plurality of the elastically stretchable members 19. Thefirst hot melt adhesive 71 may be applied to at least one of the firstsheet layer 12S and the second sheet layer 12H by slot application,curtain application or the like. Further in the case of applying thefirst hot melt adhesive 71 only to the end portions of the elasticallystretchable members 19, the first hot melt adhesive 71 may be appliedonly to the outer peripheral surfaces of the portions to be the bothends of the elastically stretchable members 19 by an application meanssuch as a comb gun or a sure wrap nozzle.

In the case of fixing the fixed end portions 19 f at the center-side inthe width direction in the intermittent stretchable region A2, inaddition to disposing the first hot melt adhesive 71 on the left andright sides individually with an interval in the width direction asillustrated in FIGS. 7 and 9, the first hot melt adhesive 71 can also becontinuously disposed over the left and right fixed end portions 19 f asillustrated in FIGS. 8 and 10.

Since the side seal portion 12A is a hardened portion by being welded byultrasonic sealing or heat sealing, when the fixed end portion 19 f onthe side seal portion 12A side is positioned in the side seal portion12A as illustrated in FIG. 18(a), the side seal portion 12A might becomeharder than necessary due to the presence of the first hot melt adhesive71 having the high holding power, that is, having hardness. Therefore,the fixed end portion 19 f on the side seal portion 12A side ispreferably adjacent to the side seal portion 12A or spaced aparttherefrom toward the center-side in the width direction as illustratedin FIG. 18(b). As can be understood from the embodiment indicated inFIG. 18(b), it is enough that adhesion sites by the first hot meltadhesive 71 may be the end portions in the stretchable direction of thestretchable regions A2 and A3 and do not need to be the both ends of theelastically stretchable members 19 as in the illustrated embodiment. Forexample, ends at least at one side of the elastically stretchablemembers 19 are not the adhesion sites by the first hot melt adhesive 71and the adhesion sites by the first hot melt adhesive 71 may be providedat appropriate positions near the ends of the elastically stretchablemembers 19.

As illustrated in FIGS. 12(d), 12(f), 12(g), 14(d), 14(g), 16(d), 16(f),and 16(g), at least a part of each adhesion site by the first hot meltadhesive 71 preferably bonds the elastically stretchable members 19 andat least one of the first sheet layer 12S and the second sheet layer 12Hwithout using the second hot melt adhesive 72 for the following reason.Even when the holding power of the first hot melt adhesive 71 is higherthan that of the second hot melt adhesive 72, in the case where thelayer of the first hot melt adhesive 71 and the layer of the second hotmelt adhesive 72 are interposed (in the case of double applications ofadhesive) between targets to be bonded, as compared with the case whereonly the layer of the second hot melt adhesive 72 is interposed, thefixing force of the elastically stretchable members 19 is high, butcohesive failure of the layer is likely to occur by the interposition ofthe layer of the second hot melt adhesive 72, and the fixing force ofthe elastically stretchable members 19 is lowered.

Therefore, it is conceivable that the first hot melt adhesive 71 and thesecond hot melt adhesive 72 are disposed so as not to overlap each otherat the passing positions of the elastically stretchable members 19 (notillustrated). However, when the positions of the first hot melt adhesive71 and those of the second hot melt adhesive 72 are different each otheras described above, it is necessary to intermittently apply the firsthot melt adhesive 71 and the second hot melt adhesive 72, and accuratecontrol of application positions of the first hot melt adhesive 71 andthe second hot melt adhesive 72 is considerably difficult.

Therefore, as illustrated in FIGS. 7 to 9 and FIGS. 11 to 16, as apreferable embodiment, the second hot melt adhesive 72 is arranged withan intermittent pattern at least in the stretchable direction, thepattern includes the positions of the fixed end portions 19 f of theelastically stretchable members 19 (for double applications ofadhesive), and the first hot melt adhesive 71 is continuously extendedin the stretchable direction with the application length longer than theapplication width of the second hot melt adhesive 72 at the passingpositions of the elastically stretchable members 19. As a result, in theapplication positions of the first hot melt adhesive 71, although doubleapplication portions by the first hot melt adhesive 71 and the secondhot melt adhesive 72 are partially formed, also single applicationportions of the first hot melt adhesive 71 are certainly formed betweenthe application portions of the second hot melt adhesive 72. Therefore,the both end portions 19 f of the elastically stretchable members 19 canbe bonded via only the first hot melt adhesive 71. In this case, thecontinuous application width 71 w of the first hot melt adhesive 71 maybe appropriately determined, but it is preferably five times or more ofthe application width 72 w of the second hot melt adhesive 72. Further,it is preferably 1.5 times or more of the interval 72 d of adjacentapplication portions in the stretchable direction of the second hot meltadhesive 72. In a usual case, it is preferable that the totalapplication width of the portions where the first hot melt adhesive 71is bonded to the elastically stretchable member 19 without using thesecond hot melt adhesive 72 is about 5 to 30 mm. As a preferableintermittent pattern of the second hot melt adhesive 72, the bondingmode being continuous in the direction intersecting the elasticallystretchable members to be described later can be exemplified.

(Sheet Bonding by Second Hot Melt Adhesive)

As long as the first sheet layer 12S and the second sheet layer 12H arebonded via the second hot melt adhesive 72 in the range at least in thewidth direction of the space between the fixed end portions 19 f of theelastically stretchable members 19, the second hot melt adhesive 72 maybe disposed in any range. However, as in the illustrated embodiment, itis preferable that the second hot melt adhesive 72 is disposed in auniform pattern throughout the stretchable regions A2 and A3 includingthe fixed end portions 19 f of the elastically stretchable members 19.

As illustrated in FIGS. 7 to 16, in the bonding mode being continuous inthe direction intersecting the elastically stretchable members, sheetbonded portions 70 to which the first sheet layer 12S and the secondsheet layer 12H are bonded via the second hot melt adhesive 72 aredisposed in a striped pattern that is intermittent in the longitudinaldirection of the elastically stretchable members 19 and continuous in adirection intersecting with the elastically stretchable members 19. Inthis bonding mode, the elastically stretchable members 19 are fixed toat least one of the first sheet layer 12S and the second sheet layer 12Hat least via the first hot melt adhesive 71 in the fixed end portions 19f, whereas the elastically stretchable members 19 are fixed to at leastone of the first sheet layer 12S and the second sheet layer 12H via thesecond hot melt adhesive 72 at intersection positions with the sheetbonded portions 70.

In this bonding mode being continuous in the direction intersecting theelastically stretchable members, along with the contraction of theelastically stretchable members 19, as illustrated in FIGS. 11(b),13(b), and 15(b), the portions positioned between the respective sheetbonded portions 70 in the first sheet layer 12S and the second sheetlayer 12H contract and are raised in the opposite directions each otherto form the pleats 80. FIGS. 11(b), 13(b), and 15(b) indicate naturallength states. The elastically stretchable members 19 are stretched fromthis state to a state stretched to some extent at the time of wearing,and as illustrated in FIGS. 11(c), 13(c), and 15(c), the hems of thepleats 80 spread. As a result, the height 80 h of the pleat 80 isdecreased. In addition, since this stretchable structure is in thebonding mode being continuous in the direction intersecting theelastically stretchable members, the pleats 80 extending straightly areformed along the sheet bonded portions 70, and air permeability andappearance are excellent.

In the embodiment illustrated in FIGS. 11 and 12, the adhesive 71 isapplied on the surface on the second sheet layer 12H side of the firstsheet layer 12S intermittently in the stretchable direction andcontinuously, with a predetermined width, in the direction intersectingwith the stretchable direction. The adhesive 71 is not applied on thesurface on the first sheet layer 12S side of the second sheet layer 12H,and the elastically stretchable members 19 are sandwiched between thefirst sheet layer 12S and the second sheet layer 12H in a stretchedstate. The first sheet layer 12S and the second sheet layer 12H as wellas the first sheet layer 12S and the elastically stretchable members 19are bonded respectively by the second hot melt adhesive 72. In thiscase, at the intersection portions of the sheet bonded portions 70 andthe elastically stretchable members 19, since the second hot meltadhesive 72 is continuous in the direction intersecting with thestretchable direction on the first sheet layer 12S side of theelastically stretchable members 19, the elastically stretchable members19 are fixed to the first sheet layer 12S via the second hot meltadhesive 72, whereas on the second sheet layer 12H side of theelastically stretchable members 19, the second hot melt adhesive 72becomes discontinuous in the direction intersecting with the stretchabledirection. In FIG. 12(e), these discontinuous portions are denoted byreference sign 73. Since the second hot melt adhesive 72 isintermittently applied in the second sheet layer 12H, a decrease inflexibility of the second sheet layer 12H, and a decrease in theflexibility as a whole of the first sheet layer 12S and the second sheetlayer 12H can be suppressed. Further, at the intersection portions ofthe elastically stretchable members 19 and the sheet bonded portions 70,although the second hot melt adhesive 72 is continues only on the firstsheet layer 12S side, on the both sides of the elastically stretchablemembers 19, the first sheet layer 12S and the second sheet layer 12H arebonded as one unit by the sheet bonded portions 70. Therefore, thecontraction force of the elastically stretchable members 19 acts on thefirst sheet layer 12S and the second sheet layer 12H almost equally, anduniform pleats can be formed on both the first sheet layer 12S and thesecond sheet layer 12H.

It is also possible to apply the second hot melt adhesive 72 to thefirst sheet layer 12S and the second sheet layer 12H with the samepattern. In this case, as illustrated in FIGS. 13 and 14, since thesecond hot melt adhesive 72 is continuous in a predetermined width, in adirection intersecting with the stretchable direction on both the firstsheet layer 12S side and the second sheet layer 12H side of theelastically stretchable members 19 at the intersection portions of thesheet bonded portions 70 and the elastically stretchable members 19,there is an advantage that the elastically stretchable members 19 can bemore firmly fixed. Although not illustrated, it is also possible thatthe second hot melt adhesive 72 is applied to the second sheet layer 12Hand not applied to the first sheet layer 12S, and the elasticallystretchable members 19 are sandwiched between both the sheet layers tobe bonded. However, in these modes, since the second hot melt adhesive72 is continuous in the second sheet layer 12H, not only thedeterioration of the flexibility of the second sheet layer 12H itself tobe brought into contact with the skin but also the deteriorated part ofthe flexibility is pressed against the skin by the elasticallystretchable members 19, and thus it is not preferable. Therefore, it isdesirable that the second hot melt adhesive 72 is not continuous on theside having the surface that contacts the skin of a wearer like thesecond sheet layer 12H as shown in the embodiment indicated in FIGS. 11and 12.

In such an embodiment, the width 70 w of each sheet bonded portion 70 inthe stretchable direction is preferably set to 0.5 to 4 mm (particularly0.5 to 1 mm), and the interval 70 d between the adjacent sheet bondedportions 70 is preferably set to 4 to 8 mm (particularly, 5 to 7 mm).Basically, if the width 70 w of the sheet bonded portion 70 in thestretchable direction is too narrow, application of the second hot meltadhesive 72 becomes difficult, whereas if the width 70 w is too wide,the flexibility reduces. Furthermore, the width 70 w in the stretchabledirection of each sheet bonded portion 70 affects the interval betweenadjacent pleats 80. As with the bonding mode being continuous in thedirection intersecting the elastically stretchable members, if thepleats 80 are formed to be thin, and the width is larger than 4 mm, aspace between the adjacent pleats 80 becomes too wide, and theindividual pleats 80 become independent in appearance. In addition, whenthe pleats 80 are deformed to collapse and spread or to fall due to acompressive force in the thickness direction, the effect of mutualsupport of the adjacent pleats 80 is reduced. As a result, resistancewith respect to the deformation and restoration after the deformationare also weaken, and the fullness becomes insufficient.

In addition, even in a case where the width 70 w of the sheet bondedportion 70 in the stretchable direction is set to 0.5 to 4 mm, if theinterval 70 d between adjacent sheet bonded portions 70 is set to lessthan 4 mm or more than 8 mm, the following situation will be caused.That is, the interval 70 d between adjacent sheet bonded portions 70affects the height 80 h and width of the pleats 80, and if the intervalbetween adjacent sheet bonded portions is about 2 mm, the pleats 80 havepoor continuity in the longitudinal direction as with the case ofcontinuously fixing in the stretchable direction (it has no meaning toprovide the sheet bonded portions 70 intermittently in the stretchabledirection). If the interval is 3 mm, the pleats 80 are extendedstraightly in the direction orthogonal to the stretchable direction, butthe effect of mutual support of the adjacent pleats 80 cannot beexpected, and fullness becomes insufficient. In addition, when theinterval 70 d between the adjacent sheet bonded portions 70 exceeds 8mm, the pleats 80 are collapsed irregularly due to the compressionduring wrapping, and the product appearance deteriorates. On the otherhand, when the width 70 w of the sheet bonded portion 70 in thestretchable direction is 0.5 to 4 mm, and at the same time, the interval70 d between the adjacent sheet bonded portions 70 is 4 to 8 mm,sufficient fullness can be finally obtained, and against the compressionduring wrapping, the pleats 80 are unlikely to be collapsed irregularly.

It is desirable that the width 70 w of the sheet bonded portion 70 isnarrow for increasing the flexibility, for example, 1 mm or less.However, due to the narrow bonded portion, it is inevitable that thefixing force of the elastically stretchable members 19 by the second hotmelt adhesive 72 is reduced, and thus it is very important to fix viathe first hot melt adhesive 71 having higher holding power at the fixedend portions 19 f as described above.

The interval 19 d between the elastically stretchable members 19adjacent to each other can be appropriately determined. However, whenthe interval exceeds 10 mm, although not to the extent of the bondingmode being intermittent in the longitudinal direction, the thickness ofthe pleats 80 changes in a direction intersecting with the stretchabledirection and causes unevenness. Therefore, in the present invention, itis preferable that the interval 19 d between the adjacent elasticallystretchable members 19 is 10 mm or less, particularly 3 to 7 mm.

The shape of the sheet bonded portion 70 (by the second hot meltadhesive 72) can be appropriately determined and may be a wave shape asillustrated in FIG. 17 or a shape extending in an oblique direction withrespect to the elastically stretchable members 19, but the shapeextending in a direction orthogonal to the elastically stretchablemembers 19 is preferable.

(Regarding the First Sheet Layer and the Second Sheet Layer)

Characteristically, either one of the first sheet layer 12S and thesecond sheet layer 12H is made of the spunbond nonwoven fabric, and theother sheet layer is made of the air-through nonwoven fabric. Theair-through nonwoven fabric has a fluffy surface on the spunbondnonwoven fabric side. In this way, when the fluffy surface having pooradhesiveness with respect to a hot melt adhesive is used intendedly asone of adhesive surfaces, and the spunbond nonwoven fabric havingexcellent adhesiveness with respect to the hot melt adhesive is used asthe other adhesive surface, even if stringiness or scattering of thesecond hot melt adhesive 72 occurs, under such insufficient adhesionconditions, the first sheet layer 12S and the second sheet layer 12H arenot bonded or are peeled off immediately even if being bonded to someextent. Therefore, deterioration of appearance of the pleats 80, whichwould be caused by the unintended adhesion, is effectively prevented. Inaddition, both of the adhesive surfaces made of the air-through nonwovenfabrics would cause a possibility that the sheet bonded portions 70 tobe bonded would not be bonded sufficiently. However, in the presentinvention, the sheet bonded portions 70 are reliably bonded by combiningwith the spunbond nonwoven fabric having high adhesiveness with respectto the second hot melt adhesive 72, and consequently, the pleats 80excellent in appearance are formed.

It can be appropriately determined which of the air-through nonwovenfabric and the spunbond nonwoven fabric is disposed on the outside andwhich of them is disposed on the inside. However, from the viewpoint ofhardly deteriorating the appearance of the pleats 80 on the outersurface of the product and being rich in flexibility when the outersurface of the product is touched with hand, it is desirable to disposethe air-through nonwoven fabric on the outside (that is, the first sheetlayer 12S in the illustrated form) and to dispose the spunbond nonwovenfabric on the inside (that is, the second sheet layer 12H in theillustrated embodiment).

The raw material fiber of the air-through nonwoven fabric and thespunbond nonwoven fabric is not particularly limited. Examples of theraw fiber include synthetic fibers such as olefin such as polyethyleneand polypropylene, polyester, and polyamide, regenerated fibers such asrayon and cupra, natural fibers such as cotton, mixed fibers andcomposite fibers in which two or more of these are used. Whenflexibility is emphasized, as at least one of the first sheet layer 12Sand the second sheet layer 12H, a nonwoven fabric of polypropylene (PP)or a copolymer thereof (for example, a copolymer in which polyethyleneor ethylene is blended as a copolymerization component) (hereinafteralso referred to as “PP type nonwoven fabric”), or a nonwoven fabric ofa sheath/core fiber (PE/PP) with polyethylene (PE) as a sheath andpolypropylene (PP) as a core component is preferably used.

Besides a single layer spunbond nonwoven fabric, a spunbond nonwovenfabric formed by laminating a plurality of spunbond layers, for example,SS nonwoven fabric (two layers) or SSS nonwoven fabric (three layers)can be suitably used, and four or more layers spunbond nonwoven fabriccan also be used.

The thickness and basis weight of the air-through nonwoven fabric andthe spunbond nonwoven fabric are not particularly limited, but it isdesirable that the thickness is 0.1 to 1 mm, and the basis weight isabout 10 to 20 g/m².

In this way, when the first sheet layer 12S and the second sheet layer12H are made of dissimilar materials, in the region forming thestretchable structure according to the present invention, the firstsheet layer 12S and the second sheet layer 12H are formed not by foldingback one sheet material, but the first sheet layer 12S and the secondsheet layer 12H are formed by using separate sheet materials. The outermember 12 of the embodiment illustrated in FIG. 5 has a first sheetmaterial and a second sheet material. In order to form the stretchablestructure of the present invention from the waist portion to theintermediate portion L, the outer member 12 of the embodimentillustrated in FIG. 5 has a first sheet material and a second sheetmaterial, as follows. The first sheet material includes an externalsurface side portion extending from the edge of the waist opening WO ofthe front body to the edge of the waist opening of the back body and afolded portion 12 r (extending so as to cover the end of the waistopening WO side of the inner member 200) folded inward at the edge ofthe waist opening WO of the front body. The second sheet material isbonded to the inside of the external surface side portion of the firstsheet material, and the second sheet material is extended from the waistportion W to the intermediate portion L. On the other hand, in the casewhere the stretchable structure of the present invention is formed fromthe under-waist portion U to the intermediate portion L except for thewaist portion as with the embodiment illustrated in FIGS. 8 and 10, thesecond sheet material is not necessarily extended to the waist portion.In this case, in a range of the waist portion, the external surface sideportion and the folded portion 12 r of the first sheet material form thefirst sheet layer 12S and the second sheet layer 12H, respectively, andin a range of the under-waist portion U and the intermediate portion L,the first sheet material and the second sheet material form the firstsheet layer 12S and the second sheet layer 12H, respectively. Further,it is not necessary to fold back the sheet material like the outermember 12 of the illustrated embodiment. Further, at least one of thefirst sheet layer 12S and the second sheet layer 12H may be partiallyformed of a sheet material different from that of other portions.

(Manufacturing Method)

In manufacturing, when the first hot melt adhesive 71 is used, the firsthot melt adhesive 71 is applied to the elastically stretchable members19 or the at least one of the first sheet layer 12S and the second sheetlayer 12H, the second hot melt adhesive 72 is applied to at least one ofthe first sheet layer 12S and the second sheet layer 12H, and theelastically stretchable members 19 are sandwiched between both the sheetlayers 12S and 12H at the same time when both the sheet layers 12S and12H are bonded.

The application method of the second hot melt adhesive 72 is notparticularly limited. However, when the width 70 w of the sheet bondedportion 70 in the stretchable direction is narrow, for example, 1 mm orless, the application width of the second hot melt adhesive 72 becomesnarrow, and the intermittent application by an application method suchas curtain or solid spraying from a nozzle becomes difficult. Therefore,it is desirable that a pattern coat suitable for narrow widthapplication (transfer of the hot melt adhesive 71 in a letterpressmethod) is used. FIG. 19 indicates an example of a manufacturing flowusing a pattern coat for applying the second hot melt adhesive 72. Inthis example of pattern coat type facilities, the elasticallystretchable members 19 are interposed between the second sheet layer 12Hand the first sheet layer 12S applied with the second hot melt adhesive72 on the surface of the second sheet layer 12H side and fed intobetween a pair of nip rolls 101 so that pressure bonding is performed toform the stretchable structure illustrated in FIGS. 11 and 12. Prior tobeing fed into the nip rolls 101, the first sheet layer 12S is broughtinto contact with an engraved roll 102 having a convex patterncorresponding to the above-described sheet bonded portions 70, that is,a striped convex pattern being intermittent on the outer circumferentialsurface in the circumferential direction (conveying direction, machinedirection: MD, a direction being the stretchable direction) and beingcontinuous in the axial direction (direction intersecting with theconveying direction, cross direction: CD), and the second hot meltadhesive 72 held on the convex pattern of the engraved roll 102 istransferred and applied. The reference sign 103 denotes a hot meltadhesive supply roll (anilox roll in letterpress printing) fortransferring and applying the second hot melt adhesive 72 to the convexpattern of the engraved roll 102 with a predetermined thickness. Thereference sign 104 denotes a supply nozzle for supplying the second hotmelt adhesive 72 to the hot melt adhesive supply roll 103.

In the illustrated embodiment, in order to dispose the first hot meltadhesive 71, which is applied for fixing the fixed end portions 19 ofthe elastically stretchable members 19, intermittently in a directionorthogonal to the elastically stretchable members 19 to overlap with theelastically stretchable members 19, the first hot melt adhesive 71 isapplied intermittently in the conveying direction from a nozzle 105,which is disposed at a position where the conveyed elasticallystretchable members are conveyed, to the outer peripheral surfaces ofthe elastically stretchable members 19, in conveying the elasticallystretchable members 19 on the upstream side of a position where pressurebonding is performed. However, by an appropriate nozzle for patterncoating, spraying, curtain application or the like, the first hot meltadhesive 71 may be intermittently applied in the conveying direction toat least one of the first sheet layer 12S and the second sheet layer12H.

(Forming of Non-Stretchable Region)

After the sheet layers 12S and 12H are bonded, and the elasticallystretchable members 19 are fixed, in a region to be the non-stretchableregion A1, the elastically stretchable members 19 are cut by applyingpressure and heating at one or more places in the middle in the widthdirection, or substantially the entire elastically stretchable members19 are finely cut by applying pressure and heating. Accordingly, theelasticity in the non-stretchable region A1 is killed while leavingelasticity in the intermittent stretchable regions A2.

FIG. 20(a) indicates the case where the elastically stretchable members19 are cut at one place in the middle in the width direction. Thiscutting process is performed with a seal roll 80 having pressurizingportions 81 each of which is provided at one place in thecircumferential direction on the outer peripheral surface of the sealroll, and each of which has a cutting convex portion 82 heated to adesired temperature, and an anvil roll 90 having a smooth surface andopposed to the seal roll 80. Then, objects to be cut, each of whichincludes the elastically stretchable members 19 disposed between thefirst sheet layer 12S and the second sheet layer 12H, are sandwichedbetween the seal roll 80 and the anvil roll 90. Thus, the elasticallystretchable members 19 are cut by pressure and heat only at the portionsnipped between the cutting convex portions 82 and the outer peripheralsurface of the anvil roll 90. In products with such processing, asillustrated in FIGS. 21(a) and 21(b), between the first sheet layer 12Sand the second sheet layer 12H in the non-stretchable region A1, onlyresidual portions of the cutting continued from the elasticallystretchable members 19 in the intermittent stretchable region A2 remainas idle elastically stretchable members 19 r, and only one melting trace22 remains as a cut mark. Although not illustrated, in the case ofcutting at a plurality of places, the seal roll 80 having the cuttingconvex portions 82 at a plurality of places in the circumferentialdirection may be used.

Further, FIG. 20(b) indicates the case where almost the entireelastically stretchable members 19 are finely and almost totally cut.This cutting process is performed with a seal roll 80 havingpressurizing portions 81 each of which is provided on an outerperipheral surface of the seal roll and each of which has a plurality ofcutting convex portions 83 arranged in a staggered shape and the likeand heated to a desired temperature. Then, objects to be cut, whichinclude the elastically stretchable members 19 disposed between thefirst sheet layer 12S and the second sheet layer 12H, are sandwichedbetween the seal roll 80 and the anvil roll 90. Thus, the elasticallystretchable members 19 are cut by pressure and heat only at the portionsnipped between the cutting convex portions and the outer peripheralsurface of the anvil roll 90. In the product subjected to suchprocessing, as illustrated in FIG. 21(c), between the first sheet layer12S and the second sheet layer 12H in the non-stretchable region A1,residual portions of the cutting continued from the elasticallystretchable members 19 of the intermittent stretchable region A2 and thecut fragments of the elastically stretchable members separated from theelastically stretchable members 19 of both the intermittent stretchableregions A2 remain intermittently in the front-back direction and thewidth direction as the idle elastically stretchable members 19 r, andthe melting traces 22 remain intermittently in the front-back directionand the width direction as cut marks.

(Sheet Bonding in Non-Stretchable Region)

Although the sheet bonded portion 70 is not necessarily provided in thenon-stretchable region A1, it is not preferable that the first sheetlayer 12S is displaced or floated with respect to the second sheet layer12H. Therefore, the first sheet layer 12S and the second sheet layer 12Hare preferably bonded. Bonding of the first sheet layer 12S and thesecond sheet layer 12H in the non-stretchable region A1 is notparticularly limited as long as the two sheet layers 12S and 12H arebonded together. However, when the bonding is performed in theabove-described bonding mode being continuous in the directionintersecting the elastically stretchable members, the idle elasticallystretchable members 19 r in the non-stretchable region A1 are fixed tothe two sheet layers 12S and 12H with the hot melt adhesive, and thus itis preferable.

From the viewpoints of ease of manufacturing and manufacturingstability, as illustrated in FIGS. 7 to 9, it is desirable that theshape, size, number, arrangement and the like of the sheet bondedportion 70 by the second hot melt adhesive 72 in the non-stretchableregion A1 are the same as those of the sheet bonded portion 70 by thesecond hot melt adhesive 72 in the intermittent stretchable region A2.Of course, the shape, size, number, arrangement and the like of thesheet bonded portion 70 by the second hot melt adhesive 72 in thenon-stretchable region A1 may be different from those of the sheetbonded portion 70 by the second hot melt adhesive 72 in the intermittentstretchable region A2.

In addition, the details of the sheet bonded portions 70 in thenon-stretchable region A1 are as described in the explanation for thesheet bonded portions 70 in the stretchable region, and hencedescription thereof will be omitted here.

<Others>

In the examples illustrated in FIGS. 7, 9 and 10, the stretchablestructure of the present invention is applied to the waist portion W,the under-waist portion U, and the intermediate portion L of theunderpants-type disposable diaper. As illustrated in FIG. 8, thestretchable structure may be applied only to the under-waist portion Uand the intermediate portion L (in the embodiment of FIG. 8, in thewaist portion W, the elastically stretchable members 19 are fixed by thefirst hot melt adhesive 71 over the entire width direction). Further, itmay be applied only to the under-waist portion U (particularly forexample, in a case where the intermediate portion elasticallystretchable member 16 is not provided). Further, the above-describedstretchable structure can also be applied to other stretchable partssuch as three-dimensional gathers, a lower torso portion of a dorsalside, leg portions, or fastening tapes of a tape type disposable diaper.

<Explanation of Terms Used Herein>

In the case where the following terms are used in the specification,those have the following meanings unless otherwise specified in thespecification.

“Front-back (longitudinal) direction” means a direction connecting theventral side (front side) and the dorsal side (back side). “Widthdirection” means a direction orthogonal to the front-back direction(right-left direction).

“Machine direction: MD” and “cross direction: CD” mean the flowdirection (MD) in manufacturing facilities and the lateral direction(CD) orthogonal to the flow direction, and either one is the front-backdirection, and the other is the width direction. The MD of a nonwovenfabric is the direction of fiber orientation of the nonwoven fabric.“Fiber orientation” is a direction along which a fiber of a nonwovenfabric runs and determined by, for example, a measurement method inaccordance with the fiber orientation test method based on the zero spantensile strength of TAPPI T481 and a simple measurement method fordetermining the fiber orientation direction from the ratio of thetensile strength of the front-back direction to that of the widthdirection.

“Spread state” means a flatly spread state without contraction orlooseness.

“Stretch rate” means the value when the natural length is taken as 100%.

“Artificial urine” is prepared by mixing urea: 2 wt %, sodium chloride:0.8 wt %, calcium chloride dihydrate: 0.03 wt %, magnesium sulfateheptahydrate: 0.08 wt %, and ion exchanged water: 97.09 wt %, and thoseare used at a temperature of 40° C. unless otherwise specified.

“Gel strength” is measured as follows: 1.0 g of super absorbent polymeris added to 49.0 g of artificial urine and the mixture is stirred with astirrer. The resulting gel is left for three hours in a thermo-hygrostatchamber at 40° C.×60% RH, and then cooled to room temperature. The gelstrength of the gel is measured with a curdmeter (Curdmeter-MAX ME-500,manufactured by 1. Techno Engineering Co., Ltd).

“Basis weight” is measured as follows. After preliminary drying a sampleor a test piece, the sample or the test piece is left in a test room orapparatus under normal conditions (the test location is at a temperatureof 20±5° C. and with a relative humidity of 65% or less) to be constantweight. The preliminary drying is to make a sample or a test piece beconstant weight in an environment having a temperature of not exceeding50° C. and a relative humidity of 10 to 25%. For fibers with an officialmoisture regain of 0.0%, preliminary drying may not be performed. Asample of dimensions (200 mm×250 mm±2 mm) is cut using a cuttingtemplate (200 mm×250 mm, ±2 mm) from a test piece in a constant weight.The basis weight is set by weighing the sample, multiplying by 20, andcalculating the weight per one square meter.

“Thickness” is automatically measured under the conditions of a load of10 gf/cm² and a pressing area of 2 cm² using an automatic thicknessmeasuring device (KES-G5 handy compression tester).

“Water absorption capacity” is measured according to JIS K7223-1996“Testing method for water absorption capacity of super absorbentpolymers”.

“Water absorption rate” is the “time to end point” when JIS K7224-1996“Testing method for water absorption rate of super absorbent polymers”has been carried out using 2 g of super absorbent polymers and 50 g ofphysiological saline solution.

“Peel strength” of the hot melt adhesive is measured as follows. Thatis, two hydrophobic spunbond nonwoven fabrics 301 composed of PP fibershaving the fineness of 1.44 dtex and a basis weight of 17 g/m² areprepared (MD 100 mm or more×CD 75 mm or more). The hot melt adhesive 302to be measured is applied with the application amount of 20 g/m²continuously in the MD with the application width of 25 mm in a centerregion in the CD of one nonwoven fabric 301. To this nonwoven fabric301, the other nonwoven fabric 301 is bonded via the hot melt adhesive302 so that they are aligned in the MD and the CD. Subsequently, anonwoven fabric adhesive body 300 illustrated in FIG. 23 is obtained bythe pressure bonding where a 2 kg roller is rolled back and forth once.Next, from this nonwoven fabric adhesive body 300, a longitudinaldirection test piece 310 and a lateral direction test piece 320 areprepared by cutting along the cutting lines indicated by dotted lines inFIG. 23 so that the longitudinal direction test piece 310 of 75 mm inthe MD×25 mm in the CD is entirely bonded and the lateral direction testpiece 320 has non-adhesive portions 321 at both sides thereof of 25 mmfrom both ends in the CD and adhesive portion 322 of 25 mm in the MD×25mm in the CD provided between the non-adhesive portions 321. In thelongitudinal direction test piece 310, as indicated by two-dot chainlines in FIG. 23, both nonwoven fabrics at one side thereof of 25 mmfrom one end in the MD are peeled off (adhesive force of an object to bebonded is lowered by cooling the object with a cold spray) to form gripmargins 311. The grip margins 311 of nonwoven fabrics are gripped withthe upper and lower grips of a tensile tester under the conditions of agrip interval of 30 mm and a test speed of 300 mm/min, and asillustrated in FIG. 24, the remaining adhesive portion 312 is peeledoff, and the force (cN/25 mm) required for peeling is measured. In thelateral direction test piece 320, a test is performed in the same manneras the longitudinal direction test piece 310, except that nonwovenfabrics of the non-adhesive portions 321 at both ends in the CD aregrasped by the upper and lower grips of the tensile tester. Then, thefailure state of a peeled portion is monitored, and at the time ofinterfacial failure (interfacial peeling) and cohesive failure, theaverage value of force at each point is taken as a measurement value bychoosing first five peaks and first five bottom points from a corrugatedportion after the start of peeling (after the curve has risen) in themeasurement curve with the vertical axis as the force. Further, at thetime of the material failure (failure of the base material), the maximumvalue of the force is taken as the measurement value. The abovemeasurements are performed three times for each of the longitudinaldirection test piece 310 and the lateral direction test piece 320, andthe measured values of three times are averaged to obtain thelongitudinal peel strength and the lateral peel strength.

“Holding power” of the hot melt adhesive is measured as follows. Thatis, as illustrated in FIG. 25, a PET film having a thickness of 25 μm iscut into two rectangular PET films 401 having a length of 100 mm×a widthof 25 mm, and the end portions in the longitudinal direction of the PETfilms (25 mm from one end in the longitudinal direction) are adhered toeach other via the hot melt adhesive layer 402 to be measured, toprepare a test piece 400. The adhesive portion 403 of the test piece 400is 25 mm×25 mm. The hot melt adhesive layer 402 is applied by slotapplication at a thickness of 20 g/m², and after bonding, a 2 kg rolleris rolled back and forth once over the adhesive portion 403 for pressurebonding. Then the test piece 400 is left under the room temperature (23°C.) for 16 hours. Further, as illustrated in FIG. 26, the both endportions of the test piece or the PET film 401 are clamped with upperand lower grips 404 tightened with screws in the thickness direction,and left in a creep tester (thermostatic chamber) for two hours at 40°C. so that a force is not applied to the adhesive portion 403.Subsequently, in the creep tester, as illustrated in FIG. 26, the upperone of the grips 404 is suspended, and a weight 405 is suspended fromthe lower one of the grips 404. A vertical load of one kilogram in total(the sum of the weight 405 and the weight-side grip 405) is applied tothe sample. The time from the start of application of load to thecomplete separation of the adhesive portion 403 or of the PET film onthe side of the weight 405 is measured. The time is measured up to 120minutes, and when the weight does not fall before 120 minutes, themeasurement result is “over 120 minutes”. The above measurement isperformed three times, and the average value of the measurement resultsis taken as the holding power (minute). As a result of threemeasurements, when one result is over 120 minutes and two results are120 minutes or less, the average value of the two measurement results of120 minutes or less is used as the holding power. When two results aremore than 120 minutes and one result is 120 minutes or less, the onemeasurement result of 120 minutes or less is taken as the holding power.When three results are over 120 minutes, the holding power is over 120minutes.

“Loop tack adhesive strength” means a value measured as follows. Thatis, a hot melt adhesive is applied at a thickness of 50 μm on a 50μm-thick PET plate. This PET plate is cut into a strip having a size of25 mm in width and 125 mm in length. Two ends of the strip areoverlapped to form a loop. After fixing this loop to the LT-100 typeloop tack tester (manufactured by Cheminstruments Inc.), the loop isbonded to a PE (polyethylene) plate in an adhesion area of 25 mm×25 mmfor an adhesion time of two seconds. Next, the loop is peeled off at 20°C. at a speed of 300 mm/min, and the maximum force is measured as theloop tack adhesive strength.

“Melt viscosity” is measured at a prescribed temperature using aBrookfield B type viscometer (spindle No. 027) in accordance with JIS Z8803.

When environmental conditions in tests and measurements are notdescribed, the tests and measurements shall be carried out in a testroom or apparatus under normal conditions (the test location is at atemperature of 20±5° C. and with a relative humidity of 65% or less).

The dimensions of each part are measured in the spread state, not thenatural length state, unless otherwise stated.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a stretchable structure and amanufacturing method therefor preferably in an underpants-typedisposable diaper as in the above example, and also in a generalabsorbent article such as a disposable diaper of a tape type or a padtype as well as a sanitary napkin.

REFERENCE SIGNS LIST

-   -   11 liquid impervious sheet    -   12 outer member    -   12A side seal portion    -   12H second sheet layer    -   12S first sheet layer    -   12 r folded portion    -   19 elastically stretchable member    -   30 top sheet    -   40 intermediate sheet    -   50 absorbent element    -   56 absorber    -   58 wrapping sheet    -   60 three-dimensional gather    -   62 gather sheet    -   70 sheet bonded portion    -   71 first hot melt adhesive    -   72 second hot melt adhesive    -   80 pleat    -   200 inner member

The invention claimed is:
 1. A stretchable structure of an absorbentarticle, comprising: a first sheet layer made of a nonwoven fabric; asecond sheet layer made of a nonwoven fabric and opposed to one sidesurface of the first sheet layer; and a plurality of elongatedelastically stretchable members provided along a stretchable directionat intervals from each other between the first sheet layer and thesecond sheet layer, wherein the first sheet layer and the second sheetlayer have sheet bonded portions bonded via a hot melt adhesive disposedin a striped pattern that is intermittent in a longitudinal direction ofthe elastically stretchable members and continuously elongated in adirection intersecting with the elastically stretchable members; whereinthe first sheet layer is made of a spunbond nonwoven fabric and thesecond sheet layer is made of an air-through nonwoven fabric; andwherein at intersection portions of the sheet bonded portions and theelastically stretchable members, the hot melt adhesive is continuous inthe direction intersecting with the elastically stretchable members on aside of the elastically stretchable members facing the spunbond nonwovenfabric, and the hot melt adhesive is discontinuous in the directionintersecting with the elastically stretchable members on a side of theelastically stretchable members facing the air-through nonwoven fabric.2. The stretchable structure of an absorbent article according to claim1, wherein the hot melt adhesive has a melt viscosity of 10,000 to40,000 mPa·s at a temperature of 140° C., a melt viscosity of 5,000 to10,000 mPa·s at a temperature of 160° C., and a loop tack adhesivestrength of 10 to 500 g/25 mm.
 3. The stretchable structure of anabsorbent article according to claim 1, wherein a width of each sheetbonded portion in the stretchable direction is 0.5 to 4 mm, and aninterval between adjacent sheet bonded portions is 4 to 8 mm.
 4. Thestretchable structure of an absorbent article according to claim 1,wherein the absorbent article is an underpants-type disposable diaper,in which an outer member disposed in a front body and a back body and aninner member attached to the outer member and including an absorber areprovided; wherein both side edges of the outer member of the front bodyand both side edges of the outer member of the back body are bonded toeach other; wherein a range corresponding in a front-back direction tothe bonded side edges is an annular lower torso portion, and a waistopening and a pair of right and left leg openings are formed; whereinthe stretchable structure is provided in a region of the outer memberlocated on both sides of the inner member in a width direction such thatthe elastically stretchable members extend along the width direction;and wherein the air-through nonwoven fabric of the second sheet layer islocated facing outwardly from a skin surface of the wearer, and thespunbond nonwoven fabric of the first sheet layer is located facinginwardly toward the skin surface of the wearer.
 5. A method ofmanufacturing a stretchable structure of an absorbent article,comprising: using a first sheet layer made of a spunbond nonwoven fabricand a second sheet layer made of an air-through nonwoven fabric;sandwiching a plurality of elongated elastically stretchable membersprovided along a stretchable direction at intervals from each otherbetween the first sheet layer and the second sheet layer, in which anair-through surface of the air-through nonwoven fabric is disposed toface a spunbond surface of the spunbond nonwoven fabric; and formingsheet bonded portions by bonding the first sheet layer and the secondsheet layer via a hot melt adhesive disposed in a striped pattern thatis intermittent in a longitudinal direction of the elasticallystretchable members and continuously elongated in a directionintersecting with the elastically stretchable members; wherein theair-through surface is fluffier and configured to have a loweradhesiveness with respect to the hot melt adhesive than the spunbondsurface; wherein in the forming of the sheet bonded portions, the hotmelt adhesive is applied to the spunbond surface of the spunbondnonwoven fabric in the striped pattern that is intermittent in thelongitudinal direction of the elastically stretchable members andcontinuously elongated in the direction intersecting with theelastically stretchable members; and wherein the hot melt adhesive isnot applied to the air-through surface of the air-through nonwovenfabric.
 6. The method of manufacturing the stretchable structure of anabsorbent article according to claim 5, wherein the hot melt adhesivehas a melt viscosity of 10,000 to 40,000 mPa·s at a temperature of 140°C., a melt viscosity of 5,000 to 10,000 mPa·s at a temperature of 160°C., and a loop tack adhesive strength of 10 to 500 g/25 mm.
 7. A methodof manufacturing a stretchable structure of an absorbent article,comprising: using a first sheet layer made of a spunbond nonwoven fabricand a second sheet layer made of an air-through nonwoven fabric;sandwiching a plurality of elongated elastically stretchable membersprovided along a stretchable direction at intervals from each otherbetween the first sheet layer and the second sheet layer, in which anair-through surface of the air-through nonwoven fabric is disposed toface a spunbond surface of the spunbond nonwoven fabric; forming sheetbonded portions by bonding the first sheet layer and the second sheetlayer via a hot melt adhesive disposed in a striped pattern that isintermittent in a longitudinal direction of the elastically stretchablemembers and continuously elongated in a direction intersecting with theelastically stretchable members; a step of applying the hot meltadhesive in which at least one of the first sheet layer and the secondsheet layer is brought into contact with an engraved roll such that acircumferential direction of the engraved roll is a stretchabledirection, and the hot melt adhesive, which is held in the stripedpattern that is intermittent in the circumferential direction andcontinuous in an axial direction on the outer peripheral surface of theengraved roll, is transferred on at least one of the first sheet layerand the second sheet layer; and a step of performing pressure bonding inwhich the elastically stretchable members are sandwiched between thefirst sheet layer and the second sheet layer on at least one of whichthe hot melt adhesive is transferred; wherein the air-through surface isfluffier and configured to have a lower adhesiveness with respect to thehot melt adhesive than the spunbond surface; and wherein in the step ofapplying the hot melt adhesive, on the outer peripheral surface of theengraved roll, an application width of the hot melt adhesive in thecircumferential direction is set to 0.5 to 4 mm, and an interval betweenthe adjacent applications of the hot melt adhesive in thecircumferential direction is set to 4 to 8 mm.
 8. The stretchablestructure of an absorbent article according to claim 2, wherein a widthof each sheet bonded portion in the stretchable direction is 0.5 to 4mm, and an interval between adjacent sheet bonded portions is 4 to 8 mm.9. The stretchable structure of an absorbent article according to claim2, wherein the absorbent article is an underpants-type disposablediaper, in which an outer member disposed in a front body and a backbody and an inner member attached to the outer member and including anabsorber are provided; wherein both side edges of the outer member ofthe front body and both side edges of the outer member of the back bodyare bonded to each other; wherein a range corresponding in a front-backdirection to the bonded side edges is an annular lower torso portion,and a waist opening and a pair of right and left leg openings areformed; wherein the stretchable structure is provided in a region of theouter member located on both sides of the inner member in a widthdirection such that the elastically stretchable members extend along thewidth direction; and wherein the air-through nonwoven fabric of thesecond sheet layer is located facing outwardly from a skin surface ofthe wearer, and the spunbond nonwoven fabric of the first sheet layer islocated facing inwardly toward the skin surface of the wearer.
 10. Thestretchable structure of an absorbent article according to claim 3,wherein the absorbent article is an underpants-type disposable diaper,in which an outer member disposed in a front body and a back body and aninner member attached to the outer member and including an absorber areprovided; wherein both side edges of the outer member of the front bodyand both side edges of the outer member of the back body are bonded toeach other; wherein a range corresponding in a front-back direction tothe bonded side edges is an annular lower torso portion, and a waistopening and a pair of right and left leg openings are formed; whereinthe stretchable structure is provided in a region of the outer memberlocated on both sides of the inner member in a width direction such thatthe elastically stretchable members extend along the width direction;and wherein the air-through nonwoven fabric of the second sheet layer islocated facing outwardly from a skin surface of the wearer, and thespunbond nonwoven fabric of the first sheet layer is located facinginwardly toward the skin surface of the wearer.
 11. The method ofmanufacturing the stretchable structure of an absorbent articleaccording to claim 6, comprising: a step of applying the hot meltadhesive in which at least one of the first sheet layer and the secondsheet layer is brought into contact with an engraved roll such that acircumferential direction of the engraved roll is a stretchabledirection, and the hot melt adhesive, which is held in the stripedpattern that is intermittent in the circumferential direction andcontinuous in an axial direction on the outer peripheral surface of theengraved roll, is transferred on at least one of the first sheet layerand the second sheet layer; and a step of performing pressure bonding inwhich the elastically stretchable members are sandwiched between thefirst sheet layer and the second sheet layer on at least one of whichthe hot melt adhesive is transferred, wherein in the step of applyingthe hot melt adhesive, on the outer peripheral surface of the engravedroll, an application width of the hot melt adhesive in thecircumferential direction is set to 0.5 to 4 mm, and an interval betweenthe adjacent applications of the hot melt adhesive in thecircumferential direction is set to 4 to 8 mm.